An example of a device for noninvasively measuring hemoglobin concentration information inside a living body is described in Patent Document 1. With this device, light is made incident inside the living body, and thereafter, light scattered inside the living body is detected by each of a plurality of photodiodes. Then, based on the intensities of the detected light components, a rate of change of the detected light amount in the direction of distance from the light incidence point is calculated. Hemoglobin oxygen saturation is calculated based on a predetermined relationship of the rate of change of the detected light amount and the light absorption coefficient. Also, based on a predetermined relationship of the temporal change of the rate of change of the detected light amount and the temporal change of the light absorption coefficient, respective concentration changes of oxygenated hemoglobin (O2Hb), deoxygenated hemoglobin (HHb), and total hemoglobin (cHb) are calculated.